Braking circuit with fluid pressure control valve

ABSTRACT

A PRESSURE CONTROL VALVE OF THE INVERTER TYPE IS EMPLOYED IN A HYDROPNEUMATIC BRAKING CIRCUIT AND COMPRISES SPACED PISTONS RECIPROCALLY MOUNTED THEREIN AND CONNECTED TOGETHER BY A ROD FOR SIMULTANEOUS MOVEMENT. SELECTIVE PNEUMATIC ACTUATION OF THE PISTONS SEQUENTIALLY OPENS AND CLOSES SPACED POPPET VALVE MEMBERS, SLIDABLY MOUNTED ON THE ROD, FOR ENGAGING A NORMALLY DISENGAGED HYDRAULIC BRAKE OR THE LIKE.

June 13, 1972 D. L. SMITH 3,669,513

BRAKING CIRCUIT WITH FLUID PRESSURE CONTROL VALVE Filed May 11, 1970 El l 17 ''IO (PP) EXH.

EXHAUST INVENTORS DONALD L. SMITH ZZQWW ATTORNEYS United States Patent 3,669,513 BRAKING CIRCUIT WITH FLUID PRESSURE CONTROL VALVE Donald L. Smith, Peoria, Ill., assignor to Caterpillar Tractor Co., Peoria, 111.

Original application Oct. 22, 1968, Ser. No. 769,482, now Patent No. 3,539,228. Divided and this application May 11, 1970, Ser. No. 48,718

Int. Cl. B60t /04 US. Cl. 303-50 16 Claims ABSTRACT OF THE DISCLOSURE A pressure control valve of the inverter type is employed in a hydropneumatic braking circuit and comprises spaced pistons reciprocally mounted therein and connected together by a rod for simultaneous movement. Selective pneumatic actuation of the pistons sequentially opens and closes spaced poppet valve members, slidably mounted on the rod, for engaging a normally disengaged hydraulic brake or the like.

This is a division of application Ser. No. 769,482, filed on Oct. 22, 1968, now US. Patent No. 3,539,228.

Numerous valves have been proposed for controlling pressurized fluid flow to an actuated device such as an automotive brake. Many such valves employ means for effecting a pilot pressure to selectively actuate the valve to communicate a pressurized fluid source to the brake. Conventional valves are oftentimes complex, costly and do not always assure efiicient operation over extended periods of time. Such problems are particularly apparent with respect to flow control valves of the inverter type which function to normally communicate full line pressure to the brake to maintain it in a disengaged condition of operation.

An object of this invention is to provide a non-complex and low-cost pressure inverting control 'valve which exhibits a high degree of structural integrity for assuring efficient operation and long service life. Such valve is particularly adapted for use as an inverter valve in a hydropneumatic circuit to normally pressurize a chamber of a hydraulic brake or the like to normally maintain it in a disengaged condition of operation. Selective actuation of the valve functions to exhaust such brake chamber to permit brake engagement.

The pressure control may comprise a rod having at least one valve member slidably mounted thereon to cooperate with a seating means to form a poppet valve for controlling fluid flow thereby. Pilot pressure control means are operatively associated with the rod to control relative opening and closing movements of the valve members and seating means. In the preferred embodiment hereinafter described, two such poppet valves are employed and two pistons are reciprocally mounted in the valve to define four consecutive and cooperating chamber means.

Other objects of this invention will become apparent from the following description and accompanying drawings wherein:

FIG. 1 schematically illustrates a hydropneumatic braking circuit employing the pressure inverting control valve of this invention therein with the valve shown in cross-section; and

FIG. 2 graphically illustrates operational pressure curves for the circuit of FIG. 1.

FIG. 1 illustrates a preferred pressure inverting control valve embodiment 10 employed as an inverter valve in a hydropneumatic braking circuit for a ground engaging vehicle or the like. It should be understood that the pressure inverting control valve principles and features herein described are adapted for other suitable applications well known in the art. For example, the valve teach ings may be utilized for the actuation of power tools or other devices which require controlled pneumatic or hydraulic operation.

The valve comprises a housing 11 having a circular flange 12 and bafile plate 13 secured in a chamber therein. The baflle and flange thus aid in defining spacedchamber portions 14 and 15 reciprocally mounting pistons 16 and 17, respectively, therein. Thus, piston 16, chamber portions 14 and 15 and piston 17 provide four consecutive chamber means for purposes hereinafter explained.

Piston 16 has a plate 18 secured thereto, located in the first or main chamber means and having a plurality of radially disposed apertures 19 formed therethrough. A rod 20 is centrally disposed in the housing and is preferably attached to pistons 16 and 17 to effect simultaneous movement thereof when one of the pistons is moved axially. The rod extends through valve seats or seating means 21 and 22 formed in piston 16 and plate 13, respectively.

A sleeve 23 is slidably mounted on the rod and has spaced first and second valve members 24 and 25, preferably poppets, suitably secured thereto with the second poppet located in the second or control chamber means. When the circuit is maintained in its normal, FIG. 1 condition of operation the conically shaped seating portion of poppet 25 will engage seat 22 whereas poppet 24 will be separated from seat 21. Since sleeve 23 is prevented from moving further rightwardly by bafile plate 13, it can be seen that piston 16 must be moved leftwardly to engage seat 21 with poppet 24.

The circuit may further comprise a conventional air compressor 26 adapted to charge an air tank 27 with supply pressure (P maintained at p.s.i., for example. A line 28 normally communicates such supply pressure to an inlet 29 communicating with the first chamber means of valve 10 to urge piston 16 rightwardly. A manually actuated directional control valve or pilot pressure control means 30, shown in its blocking or brakeif position, may be selectively actuated to communicate a variably controlled pilot pressure (P to an inlet 31. Thus, the pilot pressure in the fourth or pilot chamber means may be selectively varied by the directional control valve to precisely control the position of pilot piston 17 in the pressure inverting control valve.

The 100 p.s.i. supply pressure further communicates with a conventional relay valve 32 operatively connected to an outlet 33 of the pressure control valve to receive a control pressure (P therefrom. The relay valve functions in a conventional manner to control the desired pressure level in a pair of pneumatically actuated devices 34 and 35 preferably of the rotochamber--master cylinder type. Upon selective actuation of the latter two devices, hydraulic fluid is communicated to identical brake assemblies 37 and 38.

schematically illustrated brake assembly 37, for example, comprises a housing 39 forming a closed chamber 40 therein having an inlet 41 operatively connected to device 34. In the illustrated brake-off condition of operation, supply pressure (P substantially equals control pressure (P and communicates through line 28 and valves 10 and 32 to actuate the devices 34 and 35. Such actuation functions to pressurize chamber 40 to retract a piston 42 against the opposing force of a spring means 43. The pistons rod is connected to a brake shoe 44 which is thus maintained out of engagement with a brake drum 45. 1

During the brake-off condition of operation, supply pressure (P functions to maintain pistons 16 and 17 in their full rightward position since pilot pressure (P in the V V fourth chamber means at linet 31' is exhausted 'via valve 30. The effective or differential area of the poppet valve assembly, comprising poppets 24 and 25 and attached sleeve 23, enables the supply pressure to move the assembly fully rightwardly to close poppet 25 on seat 22. Third or exhaust chamber means communicates with exhaust to permit such seating relationship.

When the operator moves the spool of directional control valve 30 leftwardly to communicate an apportioned amount of supply pressure to the fourth or pilot chamber means, brake pads 44 will engage their respective drums in direct proportion to the amount of movement of such valve spool. It should be understood that valve 30 may be manually actuated either by hand or foot or may be automatically actuated in response to a appropriate control signal if so desired. An increase in the pressure level in the fourth chamber means, formed in part by piston 17, will function to move the piston leftwardly. Such movement will in turn shift mechanically connected rod and piston 16 leftwardly' until seat 21 engages the conically shaped seating portion of poppet 24.

Supply pressure is now cut-otf from outlet 33, but third chamber means 15 will not exhaust until a suflicient leftwardly directed transferring force is applied against the poppet assembly by the seat 21 of piston 16 to overcome the rightwardly directed reaction force on the assembly. Such transferring force may be effected by a 5 p.s.i. pilot pressure, for example, initiated in the fourth chamber means. Such initial pilot pressure represents the pressure hysteresis depicted by the abscissa of point H on brake engagement curve B in FIG. 2.

Once poppet 24 is supported on seat 21 the pistons, rod and poppet assembly will move leftwardly in unison in responseto a further increase in the pilot pressure. Such increase over 5 p.s.i. causes poppet 25 to unseat and allow the exhaust of control pressure from second chamber means 14 to third chamber means 15. The control pressure lessens until the combined leftwardly directed forces created by the pilot pressure acting on piston 17 and by the control pressure acting on the right side of piston 16 again equal the substantially constant force provided by the supply pressure in the first chamber means. As the operator continues to increase pilot pressure at inlet 31 a proportional drop in control pressure will result until the 100 p.s.i. supply pressure is balanced fully by 100 p.s.i. pilot pressure as depicted by the intersection of curve A with the axis of abscissa in FIG. 2.

When the operator returns valve towards its normal FIG. 1 position to decrease the pilot pressure, pistons and rod will move rightwardly to cause the poppet assembly to be supported at exhaust seat 22 rather than supply seat 21. Thus, the reaction force on the poppet assembly will be effectively and expeditiously transferred back to the exhaust seat. Such change preferably requires a drop of 5 p.s.i. (to 95 p.s.i.) in the pilot pressure, represented by the pressure hysteresis depicted by the abscissa of point H on brake disengagement curve D in FIG. 2.

Further reduction in pilot pressure will allow the pistons and interconnecting rod to shift-further to the right to at least partially open outlet 33 to the supply pressure when seat 21 moves away from poppet 24. The control pressure again rises until the forces on the pistons and rod are balanced and supply seat 21 again contacts poppet 24 to close such supply to second chamber means 14. A proportional increase in control pressure will result with each increment of decreased pilot pressure until the control pressure equals the supply pressure as reflected by the intersection of brake disengagement curve D with the axis inverting control valve further comprises a housing and said control means comprises a' rod mounted fof'rec'iprocal mov enients'in'said housiat least one valve member reciprocally mounted on said rod, and

seating means positioned between said first and second chamber means and operatively associated with said valve member for preventing fluid flow thereby when said valve member is seated thereon.

2. The invention of claim 1 wherein said fluid pressure actuating means comprises a pressurized fluid source, selector control valve means for selectively communicating a variable pilot pressure from said pressurized fluid source to one end of said flow control valve for controlling relative opening and closing movements between said valve member and said seating means and means for communicating said pressurized fluid source through said flow control valve when said valve memberis opened and when said selecto'r control valve means prevents f'said pressurized fluid source from communicating with the one end of said tflow control valve. v V

3. The invention of claim 1 wherein said control means further comprises at least one piston reciprocally mounted in said second chamber means of said housing, said seating means formed through said piston, saidrod engaging said piston to move said seating means into engagement 'with said valve member when said rod is moved in one direction in said housing.

4. The invention of claim 3 wherein said control means further comprises a second piston reciprocally mounted in said second chamber means of said housing, said rod further engaging said second piston for simultaneous movement with both of said pistons, said first piston separating said first and second chamber means and said second piston defining said pilot chamber means with said housing.

6. The invention of claim 4 further comprising a baffle plate attached to said housing between said pistons, a second seating means formed through said baflle plate and a second valve member slidably mounted on said rod and attached to said first valve member for simultaneous reciprocal movement therewith.

6. The invention of claim 5 wherein said control means further comprises means for communicating said pressurized fluid source to said first piston and through said flow control valve \when said one valve member is opened and when said selector control valve means prevents said pressurized fluid source from communicating with said second piston.

7. The invention of claim 6 wherein said pressure actuated device comprises braking means operatively associated with said flow control valve to be normally disengaged when exposed to fluid pressure from said pressurized fluid source and to be engaged when said selector control valve means is actuated to prevent said pressurized fluid source from communicating therewith.

8. A fluid circuit comprising a pressure control inverter valve having first, second,

third and fourth chamber means defined therein,

a pressurized fluid source communicating directly with said first chamber means,

a normally disengaged fluid actuated device operatively associated with said second chamber means,

an exhaust communicating directly with said third chamber means, and

pilot pressure control means operatively connected between said fourth chamber means and said pressurized fluid source for selectively increasing fluid pressure in said fourth chamber means for responsively decreasing fluid pressure in saidsecond chamber means, by communicating said second and third chamber means, to engage said fluid actuated device.

9. The invention of claim 8 further comprising means for momentarily delaying communication between said second and third chamber means upon initial pressurization of said fourth chamber means by said pilot pressure control means to etfect a fluid pressure hysteresis.

10. The invention of claim 8 wherein said fluid actuated device comprises a braking means, said braking means comprising spring means for engaging said braking means when said pilot pressure control means is actuated to increase fluid pressure in said fourth chamber means.

11. The invention of claim 8 wherein said pressure control inverter valve further comprises first poppet valve means disposed in said second chamber means to close communication between said first and second chamber means upon increased fluid pressure in said fourth chamber means and second poppet valve means operatively associated with said first poppet valve means for simultaneously communicating said second chamber means with said third chamber means upon increased fluid pressure in said fourth chamber means.

12. In a fluid circuit having a pressurized fluid source, a pressure control valve comprising a housing forming a chamber therein,

first and second valve members attached together for simultaneous reciprocal movement in the chamber of said housing,

a first seating means reciprocally mounted in the chamber of said housing and operatively associated with said first valve member for varying fluid flow thereby from said pressurized fluid source,

a second seating means fixedly attached to said housing and operatively associated with said second valve member for exhausting fluid thereby when said first valve member and first seating means engage, and

pilot pressure control means operatively connected between said flow control valve and said pressurized fluid source for selectively and simultaneously moving said first valve member and said first seating means relative to each other and said second valve member and said second seating means relative to each other.

13. The invention of claim 12 wherein said first and second valve members are each slidably mounted for simultaneous movement on a rod reciprocally mounted in the chamber of said flow control valve.

14. The invention of claim 13 wherein said first seating means is formed through a piston reciprocally mounted in said housing, said rod attached to said piston for simultaneous movement therewith.

15. The invention of claim 12 wherein said pressure control valve constitutes an inverter valve and further comprising a fluid actuated device operatively associated with said flow control valve for being normally disengaged when subjected directly to said pressurized fluid source when said pilot pressure control means blocks communication between said inverter valve and said pressure fluid source.

16. A fluid circuit comprising a pressurized fluid source,

a pressure control valve,

selector control valve means for selectively communicating a variable pilot fluid pressure from said pressurized fluid source to said pressure control valve and a fluid control pressure actuated device, said pressure control valve comprising a first chamber means having an inlet for communicating said pressurized fluid therein,

a second chamber means having an outlet operatively connected to said fluid pressure actuated device,

a pilot chamber means having an inlet communicating with said variable pilot fluid pressure and control means for communicating pressurized fluid from said first chamber means to said second chamber means so that the level of fluid pressure in said second chamber means is maintained inversely proportional to the level of the varied pilot fluid pressure maintained to said pilot chamber means.

References Cited UNITED STATES PATENTS 2,414,392 1/ 1947 Pickert 303-50 2,515,946 7/1950 Cadman 30354 X 3,227,494 1/1966 .Al-fieri 303- 40 DUANE A. REGER, Primary Examiner US. Cl. X.R. 188-170; 30326 

